STRIP-LINE CIRCULATOR FOR THE FREQUENCY RANGE FROM 10 TO 1,000 MHz

ABSTRACT

The strip-line circulator comprises three coplanar conductors bent about 120* and symmetrically arranged in a spaced relationship from one another about a common central area on a gyromagnetic coupling disc.

States tent 1 [111 3,838,361

Potzl [451 Sept. 24, 1974 STRIP-LINE CIRCULATOR FOR THE FREQUENCY RANGE FROM 10 TO 1,000 [56] References Cited MHZ UNITED STATES PATENTS [75] Inventor: Friedrich Potzl, Rellingen, Germany 3,341,789 9/1967 Goodman et al. 333/l.l 3,538,459 11/1970 Knerr 333/].1

[73] Assignee: U.S. Philips Corporation, New

York Primary Examiner-Paul L. Gensler [22] Filed: Sept. 14, 1973 Attorney, Agent, or Firm-Frank R. Trifari [21] Appl. No.1 397,611

[57] ABSTRACT The strip-line circulator comprises three coplanar con- [30] Foreign Application Priority Data ductors bent about 120 and symmetrically arranged Oct. 6, 1972 Germany 2249180 in a Spaced relationship from one another about a common central area on a gyromagnetic coupling 52 U.S. Cl. ..333/1.1,333/84 M disc. v [51] Int. Cl. ..H01p l/32 [58] Field of Search 333/1.1 3 Claims, 3 Drawing Figures STRIP-LINE CIRCULATOR FOR THE FREQUENCY RANGE FROM TO 1,000 MHZ The invention relates to a strip-line circulator for the frequency range from 10 to L000 MHZ comprising three two-terminal coplanar connections mutually staggered through l for supplying high-frequency electromagnetic waves, which terminals are each connected through a conductor to a common coupling space filled with a gyromagnetic material.

Such a circulator is described inter alia in US. Pat. No. 3,335,374 and German Pat. No. 1,282,754. FIG. 3 of the latter specification shows the known conventional housing. The striplines are provided between the discs made of a gyromagnetic material, which are generally referred to as microwave ferrite discs. This known arrangement further comprises the striplines and the coplanar terminals mutually staggered through 120.

As is known, one of the features of such a circulator which is of paramount importance with respect to its characteristic curves is the conditions in the coupling space, i.e., in the airgap between the two microwave ferrite discs. Whereas the device described in the German Pat. No. 1,282,754 (FIG. 2) shows wide crossing current paths, which results in that the structure has a comparatively large height and that owing to the width of the current paths the reluctance'is high, in the devices made, for example, according to the US. Pat. No. 3,335,374 comprising meshed current paths of the strip-line conductors, with a consequent reduced constructional height, are difficult to manufacture, because the crossings must be highly insulated.

Since the spacings at the crossings must be small to obtain optimum properties, such as, for example, insertion loss backward isolation and bandwidth, the known circulators are unsuitable for use at comparatively high powers because of the tendency to break down at the crossings.

It is an object of the present invention to avoid the said two disadvantages which consist in restriction to small powers in practice and in excessively high construction.

The circulator according to the invention is characterized in that the three conductors consist of identical coplanar strip conductors which bypass one another.

Each conductor may be divided into at least two ad jacent current paths. Furthermore each conductor or each current path may consist of a flat tube through which a coolant flows.

The adjacent conductors enable the height of the construction in the airgap to be a minimum. In addition, the arrangement provides the conditions for constructing a circulator for the transmission of comparatively large powers, for owing to the fact that in the coupling space crossings are completely avoided a conductor or a current path may take the shape of a flat tube, for example, a tube of rectangular section, through which a coolant flows to prevent inadmissible heating of the respective components.

Furthermore, the device is capable of withstanding higher voltages than has been the case so far. The known circulators for large powers have comparatively large spacings between the crossing conductors or current paths owing to the comparatively high voltages used. Since crossings are avoided, these comparatively large spacings between the conductors are readily obtainable and adjacent conductors or current paths may be used without the characteristics of the circulator in respect of insertion loss, bandwidth backward isolation and the like being adversely affected.

Embodiments of the invention will now be described, by way of example, with reference to the accompanying diagrammatic drawings, in which:

FIG. 1 shows an embodiment of a circulator according to the invention,

FIG. 2 shows another embodiment of a circulator according to the invention, and

FIG. 3 is a graph showing the insertion loss and isolation of a circulator according to the invention as a function of the frequency.

As has been stated hereinbefore, the circulator comprises a housing known in the art and hence not'described in further detail. The housing may have the shape shown, for example, in FIG. 3 of the German Pat. No. 1,282,754 or in FIG. 4b of the US Pat. No. 3,335,374. FIG. 1 is a plan view of a microwave ferrite disc 1. Three conductors 2 are provided on the disc which have terminals which are mutually staggered through As is shown in FIG. 1, the conductors may be terminated by connection to a common refer ence point (common earth) 5 by means of terminals or soldered connections. However, it is not necessary for the conductors to be connected to the common reference point 5. They may alternatively be connected to a common reactive element. Each terminal comprises a device 3 which includes a matching network. The matching networks are connected to coaxial plugs shown schematically by 4. The magnetic field extends at right angles to the largest dimensions of the conductors 2, as is indicated at 7.

Compared with the known designs this circulator has the advantage that crossings of the conductor 2 are avoided and the conductors are spaced from one another by a distance 6 which is determined in accordance with the required breakdown strength. The advantage of the arrangement consists in a very small structural height of the aforementioned space between the discs of gyromagnetic material. As a result, the stray inductances also may considerably be reduced. The magnetic field shown at 7 is the static magnetic field. The conductors shown in FIGS. 1 and 2 may be strip-lines cut from metal sheet or may be obtained by selective etching of copper coating on insulating substrates. The alternating inductance produced in the microwave ferrite discs 1 (for a second disc 1 is placed on top of the conductors 2) by a high-frequency alternating current which flows in a conductor 2 is rotated by the influence of the static magnetic field through an angle such that coupling to one of the two other conductors 2 only is produced.

FIG. 2 shows a circulator in which the conductors 2 are each subdivided into two current paths 8. These current paths 8 furthermore are arcuate. Otherwise the circulator of FIG. 2 is identical to that shown in FIG. 1.

FIG. 3 shows the characteristic curve of the circula' tor according to the invention, the attenuation in dB being plotted versus the frequency in MHz. A curve 9 shows the isolation and a curve 10 the insertion loss, both as a function of the frequency. The insertion loss is substantially constant between a frequency designated by 11, which for example, corresponds to I20 and in spaced relationship from one another, whereby said apex portions being directed to a common central area on said coupling means.

2. Strip-line circulator as claimed in claim 1, characterized in that each conductor is divided into at least two adjacent current paths.

3. Strip-line circulator as claimed in claim 1, characterized in that each conductor comprises a flat tube for the passage of a coolant.

1. UNITED STATES PATENT OFFIQE QERTIFICAT M Patent No. 3 838 361 v Dated September 24, 1974 xnvemofl) FRIEDRICH Po'rzL It is certified that error appeers in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

0n the title page Section [30] change "2249180" to -e-- P;224-918o.1--.,

Signed and mealed thie 26th day of November 1974.

(SEAL) Attesta McCOY M; GIBSON JR. 0. MARSHALL DANN Attes'ti Officer Cssioner of Patents 

1. A strip-line circulator including gyromagnetic coupling means adapted to be biased by a d.c. magnetic field, comprising three conductors each having an apex portion and two end portions forming an angle of substantially 120 degrees, one end portion of each conductor being a terminal for said circulator, said conductors being arranged on said coupling means in a single plane and in spaced relationship from one another, whereby said apex portions being directed to a common central area on said coupling means.
 2. Strip-line circulator aS claimed in claim 1, characterized in that each conductor is divided into at least two adjacent current paths.
 3. Strip-line circulator as claimed in claim 1, characterized in that each conductor comprises a flat tube for the passage of a coolant. 